1. Field of the Invention The present invention concerns an assembly for guiding different kinds of inspection and machining equipment around permanently installed pipes and shafts in power plants and similar locations.
2. Description of Background Art
Assemblies related to the present invention are used for guiding equipment employed in the inspection and machining of elongated objects with a circular cross section around said objects. Such equipment includes, ultrasound transducers, polishing/grinding/cutting equipment, welding torches and similar equipment. The principal application of such equipment is, e.g., in the scheduled inspections of power plant piping where the ultrasonic techniques are employed for monitoring the wear of piping walls during use. In such locations the guiding assemblies must be fitted around permanently installed piping, which prevents the mounting of said assemblies around a pipe by pushing them over the pipe from the end of the pipe, but rather, the mounting and guiding assemblies must be either permanently mounted, or alternatively, they must be capable of opening for mounting around the pipe. As the objects to be inspected are located in hard-to-reach places, the mounting and guiding assemblies must be easily mountable around the pipe.
Conventionally, these applications employ different types of segmentally linked guide rails forming a circular band that can be intimately fitted around the pipe with the help of various adjustable mounting elements. Standard equipment is then mounted on the rail of the segment which guides the equipment and provides a counter surface for the power drive elements of the guiding assembly. Different types of chains and gear elements are used as the power drive elements.
GB patent application 2,012,047 discloses an assembly comprised of a guide rail, which is mountable around the pipe, and further has cylindrical guide wheels with a center groove for the rail that are adapted to run supported by the guide rail. Supported by the wheels is adapted a transfer carriage movable by means of a chain drive. Different types of transducers and machining equipment, e.g., a welding torch, can be mounted to the transfer carriage. The guide rail is permanently mounted onto the pipe, so it cannot be transferred to different points of use, but rather, each point to be inspected must be provided with a separate, permanently fixed guide rail.
U.S. Pat. No. 4,515,018 describes an assembly in which the actual guide rail is mounted securely with the help of a separate support element to a suitable position for the measurement. The support element and the guide rail open into two parts which can be threaded around the pipe and fixed by means of locking elements. The inner perimeter of the support element has clamping means whose position can be adjusted to adapt the support element around the pipe perimeter. The adjustment span of the clamping means is relatively short, so a single support element cannot serve a larger range of pipe diameters.
The above-described apparatuses have several drawbacks. While the actual inspection procedure can be performed rapidly using fixed-rail apparatuses, the installation of the guide rails to each location to be inspected is cumbersome and expensive. For new inspection sites, such arrangements always necessitate a demanding installation phase as the guide rail must be aligned with a high precision to assure a sufficiently good repeatability of the measurement. For the above-mentioned reasons, fixed rail structures are suited to frequently repeated inspections only. Segmentally linked guiding and mounting structures are hampered by time-consuming installation at each new site. If a preadjusted mounting ring is available for each inspection site, the measurement session is carried out relatively rapidly, while the installation at a new site may take a lot of time. Such a readjustment may be necessary at pipe size transitions. Conventionally, the guiding rail is mounted around the pipe with the help of various clamping means. The adjustment span of such means is invariably small, so piping of varying size must be covered with a large selection of guiding rail assemblies.